Medical device for cutting a cornea that has a vacuum ring with a slitted vacuum opening

ABSTRACT

A medical device that can be used to cut a cornea. The device may include a blade that is coupled to a head by a blade holder. The device may also have a retention spring that exerts a force on the blade and blade holder. The head and blade can be moved across a ring by a drive assembly that contains a lead screw. The ring may contain one or more openings which have a length that is greater than a width. The openings may be coupled to a vacuum source by a tube. The vacuum pressure of the tube can be displayed by a console. The console may also have switches that allow different operating parameters to be entered through a single knob.

This application is a division of Ser. No. 09/349,835 filed Jul. 8,1999.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a microkeratome that can be used toremove tissue from a cornea.

2. Background Information

There have been developed a number of different surgical techniques tocorrect hyperopic or myopic conditions of a human eye. U.S. Pat. No.4,840,175 issued to Peyman discloses a procedure wherein a thin layer ofcorneal tissue is cut and removed from a cornea. A laser beam is thendirected onto the exposed corneal tissue in a predetermined pattern. Thelaser beam ablates corneal tissue and changes the curvature of the eye.

U.S. Pat. No. Re. 35,421 issued to Ruiz et al. discloses a device forcutting the cornea to expose an underlying surface for laser ablation.Such a device is commonly referred to as a microkeratome. The Ruizmicrokeratome includes a ring that is placed onto a cornea and a bladethat is located within an opening of the ring. The device also containsa drive mechanism which moves the blade across the cornea in a firstdirection while sliding the blade across the eye in a second transversedirection. The device can create a lamella which is flipped back so thatthe eye can be ablated with the laser.

The Ruiz microkeratome includes a head that houses the blade. The drivemechanism of the keratome moves the head and the blade across theopening of the ring. The head and ring have a pair of dovetail tongueand groove linear bearings which insure that the blade moves in a linearmanner across the cornea.

The dovetail configuration of the Ruiz microkeratome requires that thehead be loaded from the side of the ring. The surgeon must align thedovetail features before sliding the head onto the ring. Aligning thedovetail features can be difficult and awkward. It would be desirable toprovide a microkeratome that can be more readily assembled thankeratomes of the prior art.

The blade is typically assembled into a blade holder that is captured bythe head of the microkeratome. The surgeon assembles the blade into theblade holder and then loads the blade holder into an opening in thehead. To avoid contamination the surgeon typically holds the blade witha magnet.

It is important to accurately assemble the blade into the blade holderand load the blade holder into the head. A misalignment of the blade mayresult in an inaccurate cut of the cornea. It would therefore bedesirable to provide a microkeratome and a tool that insure an accurateloading of the blade.

Microkeratomes that are presently used in the field typically have astop feature that limits the movement of the blade across the cornea.The stop feature may include a pin that extends from the head andengages a stop surface of the ring. It has been found that a portion ofthe patient's eyelid may fall in between the pin and the stop surface.The eyelid may prematurely stop the head and create an inaccurate cut ofthe cornea. It would be desirable to provide a stop feature that was notsusceptible to interference from an object such as an eyelid.

Most conventional microkeratome drive mechanisms contain a plurality ofspur gears that are coupled to a single drive motor. The gears rotate tomove the blade and head across the ring to cut the cornea. Spur gearsare susceptible to wear and crowning. Additionally, the vibration of themotor may transfer to the blade through the gears and affect the cuttingaction of the blade. It would be desirable to provide a microkeratomethat was less susceptible to gear wear and crowning, and absorbed atleast some of the vibration energy generated by the motor.

The vacuum ring typically has one or more openings that are in fluidcommunication with a source of vacuum. The vacuum holds the ring inplace while the blade cuts the cornea. It has been found that theopening(s) may become occluded and prevent an adequate vacuum pressureto hold the ring in place during the procedure. Any movement of the ringduring the cutting process may result in an improper cut of the cornea.Unfortunately, the surgeon has no means to determine whether there is aninadequate vacuum pressure at the ring/cornea interface. It would bedesirable to provide a microkeratome that reduced the likelihood of anocclusion at the ring openings and provided an indication to the surgeonwhen there is inadequate vacuum pressure at the ring/cornea interface.

SUMMARY OF THE INVENTION

One embodiment of the present invention is a medical device that can beused to cut a cornea. The device may include a blade that is coupled toa head by a blade holder. The device may also have a retention springthat exerts a force on the blade and blade holder. The head and bladecan be moved across a ring by a drive assembly that contains a leadscrew. The ring may contain one or more openings which have a lengththat is greater than a width. The openings may be coupled to a vacuumsource by a tube. The vacuum pressure of the tube can be displayed by aconsole. The console may also have switches that allow differentoperating parameters to be entered through a single knob.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of an embodiment of a medical device of thepresent invention;

FIG. 2 is a cross-sectional view taken at line 2—2 of FIG. 1;

FIG. 3 is a cross-sectional view taken at line 3—3 of FIG. 2;

FIG. 4 is a cross-sectional view taken at line 4—4 of FIG. 3;

FIG. 5 is a cross-sectional view taken at line 5—5 of FIG. 3;

FIG. 6 is a side sectional view showing the device placed on a cornea;

FIG. 7 is a side sectional view showing the device cutting the cornea.

FIG. 8 is an exploded view of an alternate embodiment of a head and aring;

FIG. 9 is a cross-sectional view of the head and ring;

FIGS. 10a-c are side views showing the head being assembled to the ringtaken at line 10—10 of FIG. 9;

FIG. 11 is a perspective view of an alternate embodiment of the medicaldevice;

FIG. 12 is a perspective view showing a belt and pulley mechanism of thedevice;

FIG. 13 is a top view of a blade holder assembly of the device;

FIG. 14 is a front view of the blade holder assembly;

FIG. 15 is a side view of the blade holder assembly;

FIG. 16 is a side view showing the blade holder assembly within a headof the device;

FIG. 17 is a top sectional view of a blade loader that can be used toinsert the blade holder assembly into the head;

FIG. 18 is a side sectional view of a ring of the device;

FIG. 19 is a bottom view of a ring insert;

FIG. 20 is a top sectional view showing an alternate embodiment of thering;

FIG. 21 is a perspective view showing a stop of the device;

FIGS. 22a and 22 b are a schematic of a console for the device.

DETAILED DESCRIPTION

Referring to the drawings more particularly by reference numbers, FIGS.1-5 show an embodiment of a medical device 10 of the present invention.The device 10 may include a ring 12 that is placed onto a cornea (notshown). The ring 12 may have a port 14 which is coupled to a vacuumsource (not shown). The vacuum source may create a vacuum pressure thatpulls the ring 12 onto the cornea. The vacuum pressure prevents the ring12 from moving during a procedure.

The device 10 may have a blade 16 that is located within an opening 18of the ring 12. The blade 16 can move within the opening 18 in a firstdirection and a second transverse direction. The simultaneous movementof the blade 16 can create a cut across the surface of the eye. Thedevice 10 may include a plate 19 that is mounted to the ring 12 andwhich flattens the cornea.

The blade 16 is attached to a blade holder 20. The blade holder 20 isattached to a head 22. The head 22 and blade holder 20 both move withthe blade 16 relative to the ring 12. The blade holder 20 moves in thesecond direction while being pulled in the first direction. The head 22only moves in the first direction.

Referring to FIGS. 2 and 3, the device 10 includes a first drivemechanism 28 which moves the head 22, the blade holder 20 and the blade16 in the first direction. The first drive mechanism 28 may include afirst motor 30 that is coupled to an output shaft 32 by a gear reductionbox 34. By way of example, the motor 30 may be an electric motor. Themotor 30 may be coupled to a first gear 36 by a shaft 38 that isattached to the output shaft 32.

The first gear 36 may be coupled to a second gear 40 that is mounted tothe head 22. The second gear 40 may be connected to a third gear 42 by ashaft 44. The third gear 42 may be coupled to a gear rack 46 (see alsoFIG. 1). The first 36 and second 40 gears may be of the bevel type sothat rotation of the motor output shaft 32 imparts a correspondingrotation of shaft 44 and third gear 42. Rotation of the third gear 42along the gear rack 46 causes the head 22, blade holder 20 and blade 16to move in the first direction.

As shown in FIG. 1, the gear rack 46 may be located on a pedestal 48that is attached to the ring 12. The pedestal 48 elevates the rack 46above the cornea so that there is a low probability of an eyelashbecoming stuck in the rack and pinion gear assembly.

Referring to FIGS. 3-5, the device 10 may also have a second drivemechanism 50 that moves the blade holder 20 and the blade 16 in thesecond direction. The second drive mechanism 50 may include a secondmotor 52 which has an output shaft 54. By way of example, the motor 52may be an electric motor. The output shaft 54 may be attached to a shaft56 which has an eccentric cam pin 58. The cam pin 58 may be capturedwithin the shaft 54 by another pin 59. The eccentric cam pin 58 fitswithin a slot 60 of the blade holder 20.

Rotation of the motor output shaft 54 moves the pin 58 about the centeraxis of the shaft 56. The eccentric rotation of the pin 58 moves theblade holder 20 and blade 22 within a slot 62 of the head 22 in thesecond direction. The pin 58 slides along the blade holder slot 60 in avertical direction so that the blade 16 does not move into and out ofthe cornea.

The output shafts 38 and 56 may extend through a bulkhead 62 that ispartially located within the head 22. A collar 64 and clip 66 attach thebulkhead 62 to the head 22. The device 10 may further have a lackingring 68 for the collar 64. The motors 30 and 52 may be housed within amotor casing 69.

The first motor 30 may be connected to a first input device 70. Thesecond motor 52 may be connected to a second input device 72. By way ofexample, the input devices 70 and 72 may be foot pedals which can beoperated by a surgeon to control the actuation and speed of the motors30 and 52. This allows the surgeon to separately control the movement ofthe blade 16 in the first direction and the movement of the blade 16 inthe second direction. The surgeon can thus vary the shape and size ofthe cut.

The device 10 may further include a controller 74 which can beprogrammed to control the first 28 and second 50 drive mechanisms. Thecontroller 74 can be used in conjunction with the input devices 70 and72. The controller 74 may have programmable limit functions which limitthe speed of the motors 30 and 52.

As shown in FIGS. 6 and 7, in operation the ring 12 is placed on acornea 76. The plate 19 tends to flatten the cornea 76 adjacent to theblade 16. The surgeon actuates the first 28 and second 50 drivemechanisms to move the blade 16 in the first and second directions. Themovement of the blade cuts the cornea 76.

FIGS. 8 and 9 show linear bearings of the head 22 and the ring 12. Themedical device 10 may utilize tongue and groove bearings to couple thehead 22 to the ring 12. The tongue and groove linear bearings may beconfigured so that the head 22 can be inserted into the ring 12 from avertical direction. This is to be distinguished from the dovetailarrangements used in the prior art where the head 22 must be insertedfrom a horizontal direction.

The ring 12 may have a first sidewall 100 and a second sidewall 102. Thefirst sidewall 100 may include the gear rack 46 that is coupled to thethird gear 42 shown in FIG. 1. Each sidewall 100 and 102 may have agenerally V-shaped groove 104 and 106, respectively. The grooves 104 and106 may extend along the entire length of each wall 100 and 102.

The head 22 may have a pair of tongues 108 and 110. Tongue 108 can beinserted into groove 104. Likewise, tongue 110 can be inserted intogroove 106 so that the head 22 can slide across the ring 12. Each tongue108 and 110 preferably has a radial outer surface. The radial surface ofeach tongue 108 and 110 creates contact at two points of each V-shapedgroove 104 and 106. The two point contact aligns the tongues 108 and 110within the grooves 104 and 106 and minimizes the friction between thehead 22 and the ring 12.

Tongue 108 and groove 104 are located a distance d1 from a base surface112. The tongue 110 and groove 106 are located a distance d2 from thebase surface 112. The distance d1 may be greater than the distance d2 toprovide a keying function for the assembly of the head 22 to the ring12. The unequal distances insure that the head 22 is assembled onto thering 12 so that the third gear 42 is mated with the gear rack 46.

FIGS. 10a-c show a method for assembling the head 22 to the ring 12. Thehead 22 is moved toward the ring 12 in a vertical direction as indicatedby the arrow. A portion of the first sidewall 100 may have a chamferedsurface 114 that tapers inwardly from the gear rack 46 to the groove 104as shown in FIG. 8. Likewise, a portion of the second sidewall 102 mayhave a chamfered surface 116 that tapers outwardly from a top surface118 to the groove 106. The inward taper of the chamfered surface 114leaves sufficient area on the top surface of the first sidewall 100 forthe gear rack 46.

A surgeon can push down on the head 22 so that the tongues 108 and 110slide down the chamfered surfaces 114 and 118. The head 22 may beslightly tilted so that the tongue 108 clears the gear rack 46. The head22 can be pushed until the tongues 108 and 110 snap into the grooves 104and 106 to complete the assembly. The linear bearings of the presentinvention do not require an alignment of the tongues with the groovesand thus reduce the complexity of assembling the device.

The tongue and groove arrangement shown in FIGS. 8 and 9 may beimplemented into a surgical device which has a single motor and atransmission that couples the gears to the single motor. By way ofexample, the motor and transmission may be the same or similar to thedevice shown and described in U.S. Pat. No. Re. 35,421 issued to Ruiz etal., which is hereby incorporated by reference.

FIG. 11 shows an alternate embodiment of a medical device 200. Thedevice may include a head 202 that can move relative to a vacuum ring204. The vacuum ring 204 may have a first sidewall 206 and a secondsidewall 208. Each sidewall 206 and 208 may have a groove (not shown)that guides a corresponding linear bearing 209 of the head 202 in amanner that is the same, or similar, to the embodiment shown in FIGS.10a-c. The device 200 may include a lead screw 210 that engages an innerthread (not shown) of the first sidewall 206. Rotation of the lead screw210 will cause the head 202 to move across the ring 204.

As shown in FIG. 12, the lead screw 210 may be coupled to the outputshaft 212 of a motor 214 by a belt 216 and a pair of pulleys 218 and220. The device 200 may also have a pair of idler wheels 222 and 224that create tension in the belt 216. It is desirable to provide a motor214 that extends at an oblique angle relative to the ring 204. Theoblique angle optimizes the ergonomics for a surgeon holding the device200. The location of the idler wheels 222 and 224 compensates for theoblique angle between the motor 214 and the ring 204.

Rotation of the motor output shaft 212 will turn the pulley 220 and movethe belt 216. Movement of the belt 216 will turn the pulley 218 androtate the lead screw 210. Rotation of the lead screw 210 will move thehead 202 across the ring 204. Using a belt 216 and lead screw 210 drivemechanism has a number of advantages over the spur gear, rack and pinionarrangements used in the prior art and shown in FIGS. 6 and 7. The belt216 and lead screw 210 reduce wear and crowning. Additionally, thevibration energy may be transferred into the blade by the spur gears.The vibrating blade may create an undesirable cut of the cornea. Thebelt 216 may provide a damping element that can absorb vibration andprevent the transfer of energy into the blade.

The device 200 may include a motor 226 that can move a blade through aneccentric cam similar to the drive mechanism shown in FIGS. 4 and 5.FIGS. 13, 14, 15 and 16 show a blade holder assembly 228 that is locatedwithin the head 202. The assembly 228 may include a blade 230 that iscaptured by a blade holder 232. The blade holder 232 may have a groove234 that cooperates with a rotating eccentric cam (not shown) to imparta translational movement of the blade 230.

The assembly 228 may include an insert 236 located within an opening 238of the blade 230. The insert 236 may be constructed from a plasticmaterial that deforms when the blade 230 is pushed onto the holder 232.The deformed insert 236 may function as a retention spring that exertsspring forces 239. The spring forces prevent the blade 230 from movingrelative to the blade holder 230 during operation of the device 200.Additionally, the insert 236 may have a pair of retractable clips 240that can retain the blade 230 in the z-axis. The clips 240 deflectinward when the blade 230 is pushed onto the blade holder 232 anddeflect back out when the blade 230 is seated in the holder 232 as shownin FIGS. 14 and 15.

The insert 236 may also have a pair of spring levers 240. Each lever 241may have a protrusion 242 that can function as a bias spring to exert aspring force on a wall 244 of the head 202 when the assembly 228 isplaced within the head cavity 246. The spring force created by theprotrusions 242 will push the assembly 228 into a wall 248 of the head202. The wall 248 may be a datum zero reference surface. Pressing theassembly 228 against a datum zero wall reduces the tolerance build-up ofthe assembly.

FIG. 17 discloses a blade loader 250 that can be used to load theassembly 228 into the head cavity. The loader 250 may include a body 252with an inner cavity 254 that receives the assembly 228. The body 252may also have one or more openings 256 that are adapted to receivealignment pins 258 of the head 202. The pins 258 and openings 256 alignthe inner cavity 254 of the loader 250 with the head 202 so that theassembly 228 is accurately loaded into the head cavity.

The assembly 228 can be pushed into the head cavity 246 with a plunger260. The plunger 260 can be manually actuated. Alternatively, theplunger 260 may be automatically actuated by a solenoid or other means.The plunger 260 may have a stop 262 that can engage a surface 264 of thebody 252 to limit the movement of the assembly 228 into the head cavity246. The stop 262 can assist in centering the assembly 228 so that theeccentric cam can be inserted into the corresponding groove of the bladeholder.

FIGS. 18 and 19 show an embodiment of the ring 202. The ring 202 mayhave a tube port 270 that can receive a vacuum tube 272. The vacuum tube272 can be coupled to a source of vacuum (not shown). The device 200 mayinclude a ring insert 274 that is pressed into the ring 202. The ringinsert 274 may be constructed from a plastic material that deforms wheninserted into the ring 202.

The ring insert 274 may have a recessed outer rim 276 that cooperateswith the ring 202 to form an annular ring channel 278. The channel 278is in fluid communication with the vacuum tube 272 and a plurality ofvacuum ring openings 280, wherein air flows through the openings 280 andinto the tube 272. The openings 280 are placed adjacent to the cornea.The air flow through the openings 280 creates a vacuum pressure thatsecures the ring 202 to the cornea.

Each opening 280 preferably has a length that is greater than a width.This configuration provides an opening area sufficiently large enough tominimize pressure drops, while creating an aspect ratio that inhibitstissue occlusions within the openings 280. The slit configuration of theopenings 280 shown in FIG. 19 is less likely to occlude than a circularopening found in rings of the prior art.

FIG. 20 shows an alternate embodiment of a ring insert 274′. The ring274′ may have an oblong shaped inner opening 282. The oblong shapecreates additional space to compensate for the hinge 284 of the cornealflap 286. This allows the flap 286 to be longer and provides additionalcorneal area that can be ablated in a LASIK procedure.

FIG. 21 shows a stop mechanism 290 of the device 200. The stop mechanism290 may include a stop pin 292 that extends from the head 202. The stoppin 292 may engage a stop surface 294 of the second sidewall 208. Thestop mechanism 290 limits the length of the flap created in the cornea.The distance that the stop pin 292 extends from the head 202 can beadjusted to vary the length of the flap. The stop surface 294 is locatedabove the top surface 296 of the ring 202. Elevating the stop surface294 reduces the likelihood that an eye lash or other object may extendup into the stop mechanism 290 to impede the stop pin 292 andprematurely stop the movement of the blade.

FIGS. 22a and 22 b show a console 300 that can operate a medical device.For example, the console 300 can operate either device 10 or device 200.The console 300 may be coupled to a vacuum system 302. The vacuum system302 may include the vacuum tube 272 that is coupled to the vacuum ring(not shown). The system 302 may include a vacuum pump 304 that creates avacuum pressure in the tube 272 and an accumulator 306 that provides arelatively constant vacuum pressure within the system.

The vacuum system 302 may include a solenoid actuated pressure reliefvalve 308 that can be switched between an open position and a closedposition. In the open position the valve 308 couples the tube 272 toatmosphere to release the vacuum pressure in the system 302. The vacuumsystem 302 may also have a solenoid actuated on-off valve 310 that canbe switched between an open position and a closed position. In the openposition the valve 310 allows air to flow through the tube 272. In theclosed position the valve 310 prevents air from flowing through the tube272.

The vacuum system 302 may have a first pressure sensor 312 that is influid communication with the tube 272. The first sensor 312 providesanalog output signals on lines 314 and 316 that correspond to the vacuumpressure within the tube 272. The system 302 may also have a secondpressure sensor 318 that can sense the vacuum pressure upstream from theon-off switch 310. The second sensor 318 provides an analog outputsignal on line 320.

The console 300 may include a micro-controller 322 that can process dataand instructions in accordance with a firmware and/or hardwareroutine(s). The controller 322 may have an on-board analog to digital(A/D) converter 324 that is connected to the pressure sensor lines 314,316 and 320. The A/D converter 324 converts the analog output signalsfrom the sensors 312 and 318 to digital bit strings that can beprocessed by the controller 322.

The controller 322 can provide output signals on lines 326 and 328 toswitch the valves 308 and 310, respectively. The console 300 may includea power supply switch 330 that provides power to the valves 308 and 310through line 332. The controller 322 may switch the power switch 330with an output signal on line 334. The switch 330 may receive power froma power supply 336 through power bus 338. The power supply 336 may alsoprovide different power levels on output busses 340 and 342. By way ofexample, power bus 338 may have a voltage potential of 24 volts, powerbus 340 may have a voltage of 12 volts and bus 342 may be at 5 volts.The power supply 336 may also provide sensing output signals on lines344 and 346.

The controller 322 may be connected to display drivers 348 by line(s)350. The drivers 348 can be connected to a 7-segment light emittingdiode (LED) display 352 and/or a screen 354 by lines 356 and 358,respectively. The LED 352 and/or screen 354 can display variousalphanumeric characters such as the vacuum pressure within the tube 272.The drivers 348 may also be connected to a first indicator light 360 anda second indicator light 362. By way of example, the first indicatorlight 360 may be illuminated when there has been a reduction of vacuumthat exceeds a predetermined value. The second indicator light 362 maybe illuminated when vacuum is provided to the device 200. The indicatorlight 362 may be illuminated when the controller 322 enables the pump304 through line 364 and switches the valve 310 to the open positionthrough line 328.

The controller 322 can operate the system in accordance with a pressuresensing routing. In this routine the controller 322 reads the outputsignals of the pressure transducers 314 and 318 and may provide anumeric indicator of the pressure on the LED 352 and/or screen 354. Thecontroller 322 can also compare the pressure values with thresholdvalue(s). If the vacuum pressure within the tube 272 exceeds a thresholdvalue then the controller 322 may provide a message to this effect onthe screen 354. The console 300 may also emit an audio signal to alertthe surgeon.

The controller 322 can also provide a diagnostic routine to determinethe cause of the vacuum loss. The controller 322 can switch the on-offvalve 310 to the off position and then read the pressure from sensors312 and 318. If the pressure from sensor 318 is lower than sensor 312this may provide an indication that there is a fluid leak at the ring.The screen 354 may display a message such as RING LEAK. The controller322 may also compute a time rate of change of pressure from sensor 318.The pressure reading from sensor 312 may provide an indication that thepump 304 is malfunctioning. The sensor 312 may also provide anindication that the vacuum pump is not properly functioning even thoughthe tube appears to have an adequate vacuum pressure because of anocclusion in the ring opening(s). It is imperative that the vacuumsystem always have a vacuum pressure sufficient to maintain the positionof the ring during the cutting procedure.

The controller 322 may provide output signals on lines 366 and 368 tocontrol device motors 30, 214 and 52, 226. The signals may be providedto a 3-phase brushless DC motor driver 370 that can control the speed ofthe motors 30, 214 and 52, 226. The voltage levels of the motors can befed back to the controller 322 on lines 374 and 376. The driver 370 candetermine the actual motor speed by sensing the back emf of the motor orother means. The speed of each motor 30, 214 and 52, 226 can be providedon lines 378 and 380, respectively. The controller 322 may utilize theactual speed of each motor to provide a closed feedback control of themotors.

The speed signals may be provided to the controller 322 through a safety“watchdog” circuit 382. The circuit 382 may relay the signals to thecontroller 322 on line 384. The safety circuit 382 may receive inputsignals from the controller 322 on lines 386, 388 and 390. The circuit382 may also generate a watchdog signal on line 392. The watchdog signal392 may be provided to the driver 370 to turn off the motors and thepower switch 330 to release the vacuum in the tube 272. The relief valve308 may be normally open so that the termination of power will open thevalve 308. The on-off valve 310 may be normally closed so that atermination of power closes the valve 310.

The console 300 may also have a brushed DC motor driver 394 that isconnected to a single motor 396 that moves the blade in both directions.The driver 394 may receive input signals from the controller 322 onlines 398, 400 and 402. The speed of the motor 396 can be provided online 404. The inclusion of the driver 394 makes the console compatiblewith different types of devices including devices with either a singlemotor or two motors.

Control lines 344, 346, 374, 376, 404, 406 and 408 can be coupled to theA/D converter 324 through an analog multiplexor 410. Control line 406can provide a feedback signal from the power switch 330. The output ofthe multiplexor 410 can be provided to the A/D converter 324 on line412. The multiplexor can be selected through line(s) 414. Themultiplexor allows additional inputs to be provided to a conventional 8pin A/D converter 324. The A/D converter 324 may receive a referencevoltage on line 416. The reference voltages can be compared to determinesafety characteristics of the console.

Control line 417 is connected to a knob that can be rotated by a user.Rotation of the knob varies the voltage to the controller 322. Thevoltage can be associated with a variable parameter depending upon thestate of switches 418, 420, 422 and 424. If none of the switches 418,420, 422 or 424 are closed then the voltage of line 417 is associatedwith a maximum pre-set vacuum pressure. The controller 322 will controlthe vacuum system 302 so that the vacuum pressure does not exceed themaximum pre-set value. The maximum vacuum pressure can be adjusted byrotating the knob.

By closing switch 418 the user can adjust the volume of an audible tonecreated to warn the surgeon of an inadequate vacuum pressure. By closingswitch 420 the user can adjust the speed of motor 30, 214 and thus thetracking speed of the blade. Closing switch 422 allows the user toadjust the speed of motor 52, 226 and the cutting speed of the blade.The user can adjust the amount of vacuum loss that is acceptable beforethe indicator is activated by closing switch 424. This parameter may beused to set the threshold value for the indicator 360. The valuesassociated with motor speed, etc. may be stored in a non-volatile memorydevice such as an EEPROM 428. The switches may be located at the rearpanel of the console so that someone does not inadvertently change thesettings.

The console 300 may have another switch 426 that can be closed toinitiate the vacuum system. When this switch 426 is closed, the pump 304is enabled, the relief valve 308 is closed and the on-off valve 310 isopened. The vacuum system 302 may also be activated by depressing abutton of a foot pedal 430 that is connected to console by line 432.

The controller 322 may also be connected to a second foot pedal 434 bylines 436 and 438. The foot pedal 434 may have a pair of buttons. Onebutton can be depressed to activate the motors and cause the head tomove in a “forward” direction. The other button can be depressed to movethe head in a “backward” direction.

In operation, the surgeon can place the ring on the cornea and theninitiate the vacuum system 302 by closing switch 426 or actuating thefoot pedal 430. The surgeon can then activate the motors 30, 214 and 52,226 by actuating the foot pedal 434. The controller 322 can control themotor speed through the closed feedback loop. The controller 322 canalso monitor the pressure of the vacuum system 302 and provide anindication of both the vacuum pressure and when the pressure exceeds athreshold value. The console of the present invention thus providesinformation to the surgeon regarding the pressure of the vacuum system.

While certain exemplary embodiments have been described and shown in theaccompanying drawings, it is to be understood that such embodiments aremerely illustrative of and not restrictive on the broad invention, andthat this invention not be limited to the specific constructions andarrangements shown and described, since various other modifications mayoccur to those ordinarily skilled in the art.

What is claimed is:
 1. A medical device for cuffing a cornea, themedical device being coupled to a source of vacuum, comprising: a ringthat has a bottom surface that comes into contact with the cornea and anopening that is in fluid communication with the source of vacuum, saidopening having a slitted profile that extends along said bottom surfacewith a length dimension that is greater than a width dimension; a headthat can move relative to said ring; a blade the is coupled to saidhead; and, a motor that is coupled to said head to move said headrelative to said ring.
 2. The medical device of claim 1, wherein saidring has a center opening that has an oblong shape.
 3. A medical devicefor cutting a cornea, the medical device being coupled to a source ofvacuum, comprising: a ring that has a bottom surface that comes intocontact with the cornea and a slitted vacuum opening having a slittedprofile that extends along said bottom surface; a head that can moverelative to said ring; a blade that is coupled to said head; and, amotor that is coupled to said head to move said head relative to saidring.
 4. The medical device of claim 3, wherein said ring has a centeropening that has an oblong shape.
 5. The medical device of claim 4,wherein said ring has a center opening that has an oblong shape.
 6. Themedical device of claim 4, wherein said opening means includes a slittedopening in said ring.
 7. A medical device for cutting a cornea, themedical device being coupled to a source of vacuum, comprising: a ringthat has a bottom surface that comes into contact with the cornea andcontains opening a slitted means that extends along said bottom surfacefor allowing a vacuuming pressure to maintain said ring onto the cornea;a head that can move relative to said ring; a blade that is coupled tosaid head; and, a motor that is coupled to said head to move said headrelative to said ring.
 8. A method for attaching a medical device to acornea, comprising: placing a bottom surface of a ring onto the cornea,the ring having a slitted opening with a slitted profile that extendsalong the bottom surface; and, creating a vacuum pressure through theslitted opening in the ring.